“With rapid advance of manufacturing technology, there are many methods being developed for molding plastics into required products, such as injection molding, blow molding, hot embossing molding, compression molding, draw molding, and so on. Among which, injection molding is the most common method of plastic part manufacturing which is used to create a large variety of products with different shapes and sizes, ranged from as simple as a cup to a very complex automotive dashboard, and also ranged from as small as a watch gear weighted only 0.01 gram to a very large bathing tub weighted more than 20 kilograms. Most importantly, they can create products with complex geometry that many other processes cannot, since it is advantageous in its ability of making complex plastic parts at high production rates and high tolerances of repeatability with high precision in dimension.”
In a plastic injection molding process, a plastic material is fed into a heated barrel, melted, mixed, and forced into a mold cavity where it cools and hardens to the configuration of the mold cavity. Generally, the mold is only heated to a temperature that is lower than the glass transition point of the plastic material which is to be molded therein, so that the melted plastic is able to solidify to the configuration of the mold cavity as soon as it come into contact with the cavity surface.
In response to the smaller, thinner and lighter trend for the modern 3C products, a more advanced plastic injection molding process is in demand for satisfying the requirement of producing products configured with microstructures measured in hundreds of micrometers or even tens of micrometers, such as backlight panels, fiber optic connecters, etc., that can not be manufactured by conventional plastic injection molding as it is troubled by the molding conditions of flowability and plastic solidification while being used for manufacturing the aforesaid products configured with microstructures.
It is noted during the development of the present invention that the key for manufacturing the aforesaid products configured with microstructures by plastic injection molding relies on how to enable the mold surface temperature to change rapidly and dynamically. Moreover, it is important to keep the mold at a temperature higher than plastic's glass transition point during the procedure of filling the melted plastic into the mold, and then enable the mold temperature to drop rapidly for the purpose of reducing the total cycle time for plastic molding, by that the microstructures of high aspect ratio can be formed perfectly on the molded products with high precision.
Thus, the focal point of the present invention is how to heat up a mold in relatively short period of time and cool down the same thereafter as well.